Pros
You will lose weight, Access to tire equipment, huge discount on tires, solid bonuses for full time employees. Some awesome customers bring food for you, sometimes you get to drive cool cars, hours for part time employees are flexible.
Cons
10+ hour days. You work until the cars are done, not when the store closes. New customers let in until closing time, which CAN add up to 2 hours to your day. staying 30-45 minutes after closing is typical. People up north in snow tire country have it much worse. You may have a roof over your head, but wet tires will get you wet when it is raining outside. You have to drive some truly disgusting cars. If you don't like your fellow coworkers, your life will be miserable. Forced to shave beard everyday for the sake of the customers. Extremely fast paced work, which depending on the store location may have you constantly working with no time between cars. Some exposure to outside weather is necessary.